Fix kegtron state class for volume sensors

[Ernst79]

Proposed change

Fix for the following error, as reported in #87888

Etity sensor.kegtron_kt_200_93f5_volume_start_port_2 (<class 'homeassistant.components.kegtron.sensor.KegtronBluetoothSensorEntity'>) is using state class 'measurement' which is impossible considering device class ('volume') it is using; expected None or one of 'total_increasing', 'total'; Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+kegtron%22

I think the default state class None is ok for the the volume_start and keg_size sensors.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes Kegtron State Class Issue #87888
• This PR is related to issue: Kegtron State Class Issue #87888
• Link to documentation pull request:

Checklist

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